Locking wheel nuts and wheel bolts are commonly used to attach wheels to axel hub assemblies of automobiles and other vehicles. These fasteners are designed with security features that are intended to thwart theft by rendering the fasteners difficult to remove with conventional tools. In particular, the fasteners do not have the usual hexagonal head pattern found on conventional nuts and bolts and instead have smooth cylindrical sidewalls that cannot be gripped by standard wrenches. Fastener removal requires the use of a special security tool having a unique key pattern that matches a corresponding groove pattern formed in the fastener end face.
Additional security can be obtained by fitting a free-spinning shroud or cap over the security fasteners cylindrical sidewalls, such that the shroud is in concentric relationship therewith. The shroud discourages the use of theft devices that could otherwise be used to grip the sidewalls and remove the fastener without an authorized security tool. Because the shroud substantially surrounds all exposed surfaces of the sidewalls, no rotational purchase can be obtained in the fastener. The theft device can only engage the shroud, which freely spins under action of the theft device while the main body of the fastener remains stationary.
Various systems have been developed for rotationally retaining the shroud or spin cap on the fastener body. For example, U.S. Pat. No. 7,445,414, entitled “High Security Fastener Constructions,” is directed to a shroud fastener design having a shroud retaining system for retaining the shroud for rotation relative to the fastener body. The entire contents and disclosure of U.S. Pat. No. 7,445,414 are incorporated herein by reference. International Patent Publication No. WO2004/001237, entitled “Screw-Threaded Fastening,” is directed to a wheel nut having a fastener body and a spin cap or shroud which is retained on the fastener body by means of an outwardly flared end portion of the fastener body which is received within an undercut triangular groove in the inner surface of the cap.